Conventional office chairs are designed to provide significant levels of comfort and adjustability. Such chairs typically include a base which supports a tilt control assembly to which a seat assembly and back assembly are movably interconnected. The tilt control mechanism includes a back upright which extends rearwardly and upwardly and supports the back assembly rearwardly adjacent to the seat assembly. The tilt control mechanism serves to interconnect the seat and back assemblies so that they may tilt rearwardly together in response to movements by the chair occupant and possibly to permit limited forward tilting of the seat and back. Further, such chairs typically permit the back to also move relative to the seat during such rearward tilting.
To control rearward tilting of the back assembly relative to the seat assembly, the tilt control mechanism interconnects these components and allows such rearward tilting of the back assembly. Conventional tilt control mechanisms include tension mechanisms such as spring assemblies which use coil springs or torsion bars to provide a resistance to pivoting movement of an upright relative to a fixed control body, i.e. tilt tension. The upright supports the back assembly and the resistance provided by the spring assembly thereby varies the load under which the back assembly will recline or tilt rearwardly. Such tilt control mechanisms typically include tension adjustment mechanisms to vary the spring load to accommodate different size occupants of the chair.
Additionally, conventional chairs also may include various mechanisms to control forward tilting of the chair and define a selected location at which rearward tilting is stopped.
Additionally, such chairs include a pneumatic cylinder which is enclosed within a base of the chair on which the tilt control mechanism is supported. As such, the pneumatic cylinder is selectively extendable to vary the elevation at which the tilt control mechanism is located to vary the seat height. Such pneumatic cylinders include conventional control valves on the upper ends thereof and it is known to provide pneumatic actuators which control the operation of the valve and thereby allow for controlled adjustment of the height of the seat.
It is an object of the invention to provide an improved tilt control mechanism for such an office chair.
In view of the foregoing, the invention relates to an office chair having an improved tilt control mechanism which controls rearward tilting of the back assembly relative to the seat assembly.
The tilt control mechanism of the invention incorporates a tension adjustment mechanism which cooperates with a pair of coil springs that defines the tilt resistance being applied to the chair uprights. A tension adjustment mechanism includes a cam wedge on the spring legs of the spring which cam wedge is movable upwardly and downwardly to vary the spring load being applied by the coil springs. This cam wedge has an arcuate surface that cooperates with a pair of drive blocks. These drive blocks are mounted on a common threaded shaft which extends laterally across the tilt control mechanism and are movable toward each other and away from each other. These drive blocks have curved surfaces which face upwardly in contact with the wedge. When the drive blocks are driven together, the wedge is driven upwardly to increase tilt tension, and when the drive blocks are moved apart from each other, the wedge moves downwardly to reduce the tilt tension. This mechanism provides an improved tension adjustment mechanism that is easier to actuate for the occupant.
Other objects and purposes of the invention, and variations thereof, will be apparent upon reading the following specification and inspecting the accompanying drawings.
Certain terminology will be used in the following description for convenience and reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the arrangement and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.